Cleaning of Blast Furnace Gas Jan22

Cleaning of Blast Furnace Gas...

Cleaning of Blast Furnace Gas The process of liquid iron production in the blast furnace (BF) generates gas at the furnace top which is an important by-product of the BF process. This top gas of the blast furnace is at the temperature and pressure existing at the BF top and usually contaminated with dust and water particles. This top gas is having substantial calorific value and is known as raw BF gas or contaminated BF gas. The composition and quantity of this top gas depend on the nature of the technological process in the blast furnace and the type and the quality of the raw materials used for the iron production in the blast furnace. In order to further use the raw BF gas, it is necessary to clean it by using certain process systems which reduces its content of the solid particles. The top gas contains carbon mono oxide (CO) and is known as blast furnace gas after its cleaning. It is used as fuel gas for heating blast air in the hot blast stoves as well as supplemental fuel in the steel plant. For the BF gas to be used as fuel gas, it is necessary that the raw BF gas is cleaned and cooled to reduce gas volumes and moisture content. Prior cooling and reduction in gas volume is also necessary since it results in substantial savings in delivery costs throughout the extensive distribution system of the steel plant. Typical analysis of the blast furnace gas for a blast furnace operating with pulverized coal injection (PCI) is given in Tab 1. The process systems for the gas cleaning are either wet gas cleaning system or dry cleaning system. High-efficiency gas cleaning systems are vital for the reliable operation and long campaign...

Factors affecting Coke rate in a Blast Furnace Jun29

Factors affecting Coke rate in a Blast Furnace...

Factors affecting Coke rate in a Blast Furnace  BF is a counter current reactor in which the reducing gas is produced by the gasification of the carbon of the BF coke with the oxygen of the hot blast injected via tuyeres in the lower part of the furnace. The reducing gas flows upwards reducing the iron bearing burden materials charged at the top of the furnace. Coke rate is the parameter for the consumption of BF coke which is measured in kilograms of BF coke consumed per ton of hot metal produced. Blast furnace (BF) coke is a key material for BF ironmaking, acting as a major energy source (fuel), a reductant, a carburization agent and a permeable structural support. There is no other satisfactory material available, which can replace, fully or partially, BF coke as a permeable support of blast furnace charge. BF coke is the most important raw material fed into the blast furnace in terms of its effect on blast furnace operation and hot metal quality. A high quality BF coke is able to support a smooth descent of the blast furnace burden with as little degradation as possible while providing the lowest amount of impurities, highest thermal energy, highest metal reduction, and optimum permeability for the flow of gaseous and molten products. Introduction of high quality BF coke to a blast furnace results in lower coke rate, higher productivity and lower hot metal cost. Role of coke in improving the BF performance is shown at Fig 1. Fig 1 Role of coke in improving BF performance A realistic assessment of the likely performance of coke in the blast furnace operating with or without injection technology includes those properties of coke that reflect its resistance to degradation under the chemical and...

Blast Furnace Gas Top Pressure Recovery Turbine Jun24

Blast Furnace Gas Top Pressure Recovery Turbine...

Blast Furnace Gas Top Pressure Recovery Turbine  Modern blast furnaces in steel plants operate at a high top gas pressure. The blast furnace (BF) gas leaving the BF at the top still maintain a pressure of around 1.6 kg/sq cm (g) to 3 kg/sq cm (g) and has a temperature of around 200 deg C.  This BF gas which is coming out at the top of a BF is cleaned to remove dust and the cleaned gas is used in the steel plant as a fuel for heating purpose at a relatively low pressure. In the process, a large amount of pressure energy is lost across the valve. BF gas top pressure recovery turbine (TRT) is a mechanism that utilizes the BF gas heat and pressure energy to drive a turbine.  The work generated by the turbine is transferred to a generator and converted to electric power. TRT generates power by exploiting a known property of all gases which is the expansion of gas volume with the reduction of its pressure. The system comprises dust collecting equipment, a gas turbine, and a generator. TRT is basically an energy saving measure at the BF which utilizes the waste pressure energy of the BF top gas to generate electric power. A TRT unit can produce around 15 to 60 kWh/t of hot metal (HM). Its output can meet around 30 % of the power needed by the all equipment (including the air blower) of the BF. The BF gas leaving the TRT unit can still be used as fuel in the steel plant. During iron making process, BF gas with high pressure and temperature is produced in blast furnace. In conventional practice, the energy of BF gas is wastage by pressure reduction at septum valve. Equipping TRT...

Fuel gases used in steel industry...

Fuel gases used in steel industry Fuel gas is a fuel which under ordinary conditions is in the form of gas. Fuel gases are used in steel plants for different applications which include (i) a source of heat (ii) as a reductant and (iii) cutting and welding application. Fuel gases usually used in steel industry are natural gas (NG), liquefied petroleum gas (LPG), acetylene, by product gases (blast furnace gas, coke oven gas and converter gas). Natural gas Natural gas is a gaseous fossil fuel which is extracted from deposits in the earth. It is a mixture of hydro carbons consisting primarily of methane (generally greater than 80 %) but includes varying amounts of other higher alkanes such as ethane, propane and butane etc. It may even contain some small percentage of nitrogen, carbon dioxide and hydrogen sulphide. It is an odorless, colourless, tasteless and non toxic gas. Natural gas is lighter than air and it burns with a clean blue flame when mixed with the requisite amount of air and ignited. It is considered one of the cleanest burning fuels. On burning it produces primarily heat, carbon dioxide and water. Quantities of natural gas are measured in normal cubic meters (corresponding to 0 deg C and I Kg/Sq cm pressure) or standard cubic feet (corresponding to 16 deg C and 14.73 psia pressures). The higher heat value of one cubic meter of natural gas varies from around 9500 Kcal to 10,000 Kcal. Its density is around 0.85 Kg/Cum. The main usage of natural gas in the steel industry is in iron making. For production of direct reduced iron it is reformed to produce reducing gases which are then used for the reduction of iron ore. The main reforming reactions are as follows. 2CH4...

Blast Furnace gas generation and usage Mar18

Blast Furnace gas generation and usage...

Blast Furnace gas generation and usage Blast furnace (BF) gas is a gaseous by product which is generated while producing hot metal (liquid iron) in a blast furnace. The operation of the blast furnace is controlled to produce hot metal of a specified quality and during this production BF gas comes out from the furnace top. During production of hot metal in a blast furnace, hot air blast is blown in the furnace through the tuyeres. The oxygen of the blast reacts with the coke. The gas produced by this reaction moves up the furnace shaft which has been charged with ores, fluxes and coke. After a number of chemical reactions and a travel of around 25-30m the BF gas comes out of the furnace as a heated, dust laden and lean combustible gas. Around 1500-1700 Cu m/ton of hot metal of BF gas is generated during the process. Though the purpose of partial combustion of carbon in a blast furnace is to remove the oxygen from the ore but the volume of gas generated in a blast furnace makes the blast furnace as a gas producer. The percentage of CO and CO2 in BF gas is directly related to the amount of carbon in the charged coke and amount of CO2 in the charged flux (Limestone and dolomite). The coke rate (The rate of carbon consumption) in the blast furnace depends mainly upon the type of the hot metal to be made, the chemical and the physical characteristics of the charged materials, the distribution of the materials in the furnace stack, the temperature and the oxygen enrichment of the hot air blast. The total amount of CO+CO2 gases by volume in the BF gas at the furnace top is around 40% of the...